Implement filling a path with nv_path_rendering cover

Implement filling a path with nv_path_rendering cover functionality.

The nv_path_rendering cover can be used if the fill is non-inverted
and the draw operation does not require use of vertex shaders.

Moves code for the inverted fill from GrStencilAndCoverPathRenderer
down to GrGpuGL.

R=bsalomon@google.com, markkilgard@gmail.com, cdalton@nvidia.com

Author: kkinnunen@nvidia.com

Review URL: https://codereview.chromium.org/22686002

git-svn-id: http://skia.googlecode.com/svn/trunk/include@11667 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/GrTypes.h b/gpu/GrTypes.h
index 80cfca3..ff8f442 100644
--- a/gpu/GrTypes.h
+++ b/gpu/GrTypes.h
@@ -608,6 +608,7 @@
     kProgram_GrGLBackendState          = 1 << 8,
     kFixedFunction_GrGLBackendState    = 1 << 9,
     kMisc_GrGLBackendState             = 1 << 10,
+    kPathRendering_GrGLBackendState    = 1 << 11,
     kALL_GrGLBackendState              = 0xffff
 };